On Tue, 22 Sep 2020 16:27:03 +0200 "Jürgen Groß" <jgross@xxxxxxxx> wrote: > On 22.09.20 16:15, SeongJae Park wrote: > > From: SeongJae Park <sjpark@xxxxxxxxx> > > > > Persistent grants feature provides high scalability. On some small > > systems, however, it could incur data copy overheads[1] and thus it is > > required to be disabled. It can be disabled from blkback side using a > > module parameter, 'feature_persistent'. But, it is impossible from > > blkfront side. For the reason, this commit adds a blkfront module > > parameter for disabling of the feature. > > > > [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability > > > > Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx> > > --- > > .../ABI/testing/sysfs-driver-xen-blkfront | 9 +++++++++ > > drivers/block/xen-blkfront.c | 20 ++++++++++++++----- > > 2 files changed, 24 insertions(+), 5 deletions(-) > > > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkfront b/Documentation/ABI/testing/sysfs-driver-xen-blkfront > > index c0a6cb7eb314..9c31334cb2e6 100644 > > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkfront > > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkfront > > @@ -8,3 +8,12 @@ Description: > > is 32 - higher value means more potential throughput but more > > memory usage. The backend picks the minimum of the frontend > > and its default backend value. > > + > > +What: /sys/module/xen_blkfront/parameters/feature_persistent > > +Date: September 2020 > > +KernelVersion: 5.10 > > +Contact: SeongJae Park <sjpark@xxxxxxxxx> > > +Description: > > + Whether to enable the persistent grants feature or not. Note > > + that this option only takes effect on newly created frontends. > > + The default is Y (enable). > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > > index 91de2e0755ae..b2d3b1262404 100644 > > --- a/drivers/block/xen-blkfront.c > > +++ b/drivers/block/xen-blkfront.c > > @@ -1866,8 +1866,8 @@ static int talk_to_blkback(struct xenbus_device *dev, > > message = "writing protocol"; > > goto abort_transaction; > > } > > - err = xenbus_printf(xbt, dev->nodename, > > - "feature-persistent", "%u", 1); > > + err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", > > + info->feature_persistent); > > if (err) > > dev_warn(&dev->dev, > > "writing persistent grants feature to xenbus"); > > @@ -1941,6 +1941,13 @@ static int negotiate_mq(struct blkfront_info *info) > > } > > return 0; > > } > > + > > +/* Enable the persistent grants feature. */ > > +static bool feature_persistent = true; > > +module_param(feature_persistent, bool, 0644); > > +MODULE_PARM_DESC(feature_persistent, > > + "Enables the persistent grants feature"); > > + > > /** > > * Entry point to this code when a new device is created. Allocate the basic > > * structures and the ring buffer for communication with the backend, and > > @@ -2007,6 +2014,8 @@ static int blkfront_probe(struct xenbus_device *dev, > > info->vdevice = vdevice; > > info->connected = BLKIF_STATE_DISCONNECTED; > > > > + info->feature_persistent = feature_persistent ? 1 : 0; > > Just use the value. Yes, I will. > > With that changed: > > Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Appreciate :) Thanks, SeongJae Park
